To Sense or Not To Sense: A Comparative Study of Energy Efficiency in Energy-Aware Random Access Networks

With the rapid proliferation of low-power machine-type devices (MTDs) in the Energy-Aware Internet of Things (EAIoT), a central challenge for IEEE 802.15.4-based wireless sensor networks is to maximize device lifetime while ensuring reliable data delivery. This paper addresses this challenge by proposing a general and practical energy model that facilitates the analysis of energy efficiency in both Carrier Sense Multiple Access (CSMA) and Aloha networks, and solves a constrained optimization problem: maximizing network lifetime under a lifetime throughput constraint. In particular, by jointly considering finite energy budgets, carrier sensing time, data traffic, and various power consumption levels, we derive closed-form expressions for the lifetime and lifetime throughput of MTDs operating under both CSMA and Aloha. Our analysis reveals a nuanced relationship: while a fundamental trade-off exists in saturated conditions, a win-win situation that enhances both lifetime and lifetime throughput emerges in the unsaturated regime. Building on this, we derive the optimal lifetime for both protocols under the lifetime throughput constraint, which facilitates a systematic comparative study. This comparison identifies when, and to what extent, carrier sensing can significantly improve MTDs’ lifetime while ensuring reliable packet delivery. The proposed analyses are validated through extensive simulations and a case study on IEEE 802.15.4-based networks, providing pivotal insights for the practical design of energy-efficient access protocols.